The present invention relates to a replacement heart valve simulator with an accelerated wear and fatigue tester, in which the rate and type of testing may be varied, and in which the suitability of replacement heart valves for particular humans may be evaluated.
Existing systems for testing heart valves for use as replacements in humans provide means to pulse fluids, such as water, through the replacement valve to test the operation and life of such valves in vitro. One method provides a control valving arrangement to provide an alternating air pressure and vacuum against a diaphragm exposed to the liquid, in order to move the diaphragm first in one direction and then the other direction against the liquid to cause the liquid to pulse the valve. Such arrangements have tended to buckle and distort the diaphragm, which have introduced anomalies into stress measurements which may be undertaken on the replacement valve being tested. In addition, various mechanical arrangements have been proposed and used to apply a pressure to the diaphragm using an eccentric and variable-stroke motor driven apparatus requiring complex linkage arrangements and drive systems. However, such arrangements have proved to be noisy, providing problems in the acoustical testing of the operation of the replacement heart valves. In addition, the various existing arrangements normally provide on-off or square wave pulsing, or a mechanical sinusoidal input signal provided through use of a crank and piston arrangement.
However, it is desirable to be able to selectively apply a variety of input signals in the testing of such valves, including pulsed, sinusoidal, triangular and random signals, to be able to control the phasing of multiple signals, and further including signals recorded from an actual heart, in order to more closely simulate or reproduce the fluid flow conditions which may be encountered in the operation of a human heart. In addition, it is desirable to be able to simulate an arrhythmic heart, and also to be able to accurately and directly control the pressure applied to the heart valve being tested so as to be able to provide a wide range of test pressures.
Still further, it is desirable and often necessary to be able to accelerate the testing of the replacement heart valves to accomplish necessary testing in available or reasonable time periods.
In addition, it is desirable to be able to predict potential irregularities in an implanted in vivo replacement heart valve by monitoring and comparing its operation with a response database compiled by recording the operation of in vitro replacement heart valves and noting operational characteristics prior to development of irregularities.